Sentry (monitoring system)
Sentry is a highly automated collision monitoring system that continually scans the most current asteroid catalog for possibilities of future impact with Earth over the next 100 years.[1] Whenever a potential impact is detected it will be analyzed and the results immediately published on the Near Earth Object Program.[1]
Two or three weeks of optical data is not enough to conclusively identify an impact years in the future.[2] By contrast, eliminating an entry on the risk page is a negative prediction; a prediction of where it will not be.[2] From the point of view of the general public, it isn't worth getting worried about an object with a couple weeks of optical data showing a possible Earth encounter years from now.[2]
The Impact Risk page lists a number of lost objects such as 2004 BX159 that are, for all practical purposes, permanent residents of the risk page; their removal may depend upon a serendipitous rediscovery.[3] 1997 XR2 was serendipitously rediscovered in 2006 after being lost for more than 8 years. Some objects on the Sentry Risk Table, such as 2000 SG344, might even be man-made.
Notable objects on the risk page include (numbered asteroids listed first): (29075) 1950 DA, 99942 Apophis, 101955 Bennu, 2007 VK184, 2009 FD, 2008 CK70, 1994 WR12, 2010 RF12, and 2013 BP73.[1]
The diameter of most near-Earth asteroids that have not been studied by radar or infrared can generally only be estimated within about a factor of 2 based on the asteroid's absolute magnitude (H).[1] Their mass, consequently, is uncertain by about a factor of 10. More than two dozen known asteroids have higher than a one in a million chance of impacting into Earth within the next 100 years.[4]
In August 2013, the Sentry Risk Table started using planetary ephemeris (DE431) for all NEO orbit determinations.[5] DE431 (JPL small-body perturber ephemeris: SB431-BIG16) better models the gravitational perturbations of the planets and includes the 16 most massive main-belt asteroids.[5]
References
- ^ a b c d "Sentry Risk Table". NASA/JPL Near-Earth Object Program Office. 14 Oct 2011. Retrieved 2011-10-14.
- ^ a b c Jon Giorgini (30 July 2002). "Understanding Risk Pages". Columbine, Inc. (hohmanntransfer). Retrieved 2011-11-21.
- ^ "IMPACT RISK ASSESSMENT: AN INTRODUCTION". NASA/JPL Near-Earth Object Program Office. 31 Aug 2005. Retrieved 2011-10-14.
- ^ Donald K. Yeomans (9 February 2013). "Beware of Errant Asteroids". New York Times. Retrieved 10 February 2013.
{{cite web}}: External link in|author= - ^ a b "Sentry Notes". NASA/JPL Near-Earth Object Program Office. 2013-Aug-12. Retrieved 2013-08-26.
{{cite web}}: Check date values in:|date=(help)
External links
- SENTRY - An Automatic Near-Earth Asteroid Collision Monitoring System@ neo.jpl.nasa.gov
- IMPACT RISK ASSESSMENT: AN INTRODUCTION
- Sentry Risk Table
- NEODyS CLOMON2
- List of objects for which all previously detected potential impacts have been eliminated
 | This article related to the National Aeronautics and Space Administration is a stub. You can help Wikipedia by expanding it. |